PART 1 GARTH : PACIFIC OXYRHYNCHA 75 



Bay, 51 fathoms, Albatross (Rathbun, 1898) ; Gulf of California: north- 

 west of Cape Tepopa, 145 fathoms, Albatross (Rathbun, 1925) ; Santa 

 Inez Bay, 33-35 fathoms, Zaca (Crane). 



Atlantic analogue: Collodes rostratus A. Milne Edwards. 



Diagnosis: Rostrum a tuberculate spine arising from a dome-shaped 

 base; a similar abdominal spine posteriorly directed. Carapace heavily 

 and unevenly granulate, especially on branchial regions; one gastric and 

 one cardiac spine or tubercle. Postorbital tooth large, anterior margin 

 straight or slightly concave. Basal antennal article with inner lamina, 

 outer margin coarsely denticulate. Fingers of adult male gaping widely 

 at base. Tip of male first pleopod slender, lateral lobe not prominent. 



Description: Carapace slightly pubescent; unevenly granulate with 

 unequal granules, the largest ones on the summit of the branchial 

 regions, which have the greatest number of granules; a few small 

 granules on cardiac and gastric regions; more on the hepatic regions; 

 lateral and posterior margins covered with small granules. Four median 

 capitate spines, one at end of rostrum, one gastric, one cardiac, and one 

 directed obliquely backward and upward on the first abdominal seg- 

 ment. A supraorbital tubercle; a rather broad postorbital lobe directed 

 obliquely forward. Basal antennal segment with a prominent inner 

 lamina ending in a lobe and an outer margin cut into numerous denticles. 

 The male sternum granulate on the cheliped segment near the abdomen 

 and especially on the most protuberant parts ; granules few on other 

 segments except close to abdominal cavity. Female abdomen roughened 

 with numerous but separated granules. 



Chelipeds slender; outer margin of merus armed with about eight 

 stout spinules, other margins finely spinulous, also the inner margin of 

 the carpus ; manus nearly smooth ; fingers narrowly gaping in basal half. 

 Legs long-hairy, the hairs retaining large quantities of mud. (Rathbun, 

 1925) 



The diagnosis above applies to mature specimens. The bifid rostrum 

 of the very young persists in some individuals up to 10-12 mm and 

 may be retained as a bituberculate tip to the single spine in even the 

 largest specimens. While the old are very granulate and tuberculate, 

 the young may be almost as smooth of carapace as Collodes tumidus. 

 Considerable variation exists with respect to the cardiac spine, which 

 may be upstanding, as in the case of typical C. granosus, or reduced to 

 a tubercle. However, the spine on the first abdominal segment is always 

 present and always elongated, and, along with the difference in curvature 



